The invention relates to gas bag folding as well as to a method and device for folding the gas bag.
From DE 44 22 276 A1 a gas bag is known for an airbag module wherein the gas bag has main folds which run at least in part along closed paths round an imaginary centre on the substantially empty outspread gas bag. The closed main folds preferably describe circular paths or ellipses of slight eccentricity. The folds run mainly at right angles to the plane in which the gas bag is spread out prior to folding. The gas bag has an upper part and a lower part which are folded together.
This path of the main folds has the advantage that the folded gas bag can be opened quickly and easily. More particularly during the unfolding of a gas bag of this kind there is not the danger that the inner pressure produced in partial areas of the gas bag will impede the opening of further folds. This gas bag can thereby be used for driver, passenger and side airbags.
Furthermore a passenger airbag is known from EP A 0 619 204 wherein the gas bag has in the weft direction two adjoining fold layers between which an interspace is to be provided which runs in the weft direction. Since this interspace is however in practice not present in the folded position of the gas bag in the airbag module and rather the adjoining fold layers even engage in each other when pressed together as required for stowage, unfolding the gas bag becomes difficult.
The object of the invention is to reduce the time for the unfolding of the gas bag.
With a gas bag for an airbag module which is folded in the non-activated state and has a closed upper side and a lower side having a blow-in mouth or an opening for inserting a gas generator into the gas bag wherein at least one fold is provided in each of the two sides and extends at right angles to same, according to the invention, each fold of one side is separated from each opposite fold of the other side. Experiments have shown that through this separate arrangement of the folds it is possible to achieve an extremely quick unfolding of the gas bag.
In a preferred embodiment the upper side and the lower side each have an outer and an inner main fold. The outer main fold is designated the fold visible on the upper and lower side of the folded gas bag whilst the inner main fold is that which is opposite the main fold of the relevant other part inside the folded gas bag.
The folds preferably run so that the inner main folds of the upper side and lower side contact one other at least linearly.
The folds preferably run so that the inner main folds of the upper and lower sides contact one another on a straight or circumferential line wherein the circumferential line runs in a ring or coil shape. The fold layer between the inner and outer main folds preferably runs substantially at right angles to the plane of the outspread empty airbag.
In a preferred embodiment several outer main folds and several inner main folds are provided which contact one another on circumferential ring-shaped lines.
Furthermore the folds are preferably arranged around a hollow space and the main folds of the upper side are preferably symmetrical with the main folds of the lower side. The hollow space is provided for holding a gas generator.
A method for folding an airbag, more particularly for achieving the gas bag folding described above is characterized in that the empty gas bag is spread out so that an upper and lower side are provided, that then both sides are folded separately from each other and that the folds are gathered jointly to the required size for packaging in the airbag module.
In one embodiment of the method, folding devices which run substantially at right angles to the plane of the outspread gas bag are brought from top and bottom up to the gas bag. An excess pressure is produced in the gas bag so that the gas bag is pressed between the folding devices. The excess pressure can be produced in the gas bag both before and after bringing the folding devices up to the gas bag. As a result of the excess pressure between the upper side and lower side, these sides are separated from each other and folded separately from each other between the folding plates. The folds are then compressed substantially across the folding direction. The folding devices are then removed from the gas bag. In a further embodiment it is proposed that the removal of the folding devices is carried out at the same time as an under pressure is produced in the gas bag.
A device for folding a gas bag, more particularly to produce a gas bag folding of the aforesaid form and for carrying out the method of the aforesaid kind is characterized in that the upper and lower side of an outspread gas bag are associated with separate folding devices which run at least approximately at right angles to same and which can be moved in the direction of the plane of the outspread airbag and that one excess pressure generator is provided for each which can be attached to the gas bag. In a further design an under pressure generator is further provided which can be connected to the gas bag.
In a first embodiment overlapping folding plates are provided which can be displaced towards each other. In order to produce folds which run along closed circular paths, the overlapping mutually displaceable folding plates are mounted on concentric circles. The gas bag is folded in the starting position of the folding plates in which these only slightly overlap one another. To compress the gas bag and thus fold it to the required stowage size the folding plates are pushed over each other, i.e. the overlapping becomes greater and the radius of the circles on which the folding plates lie is reduced.
In a further embodiment it is proposed that at least one spiral spring is arranged as the folding device. At least one spiral spring each is preferably mounted beneath and above the gas bag. The spiral spring is wound so that its winding layers run spaced from each other so that the gas bag when inflated during the folding process can project into this interspace. For the folding process the spiral springs are pressed against the airbag. At the end of folding and the following compression of the folds the spiral springs turn in so that their diameter reduces.
In a third embodiment at least one spiral shaped folding dish is provided as the folding device. One spiral shaped folding dish is preferably provided each above and below the gas bag. In one embodiment, several following folding dishes are provided wherein each folding dish extends preferably over an angular area of about 360 degs.
With the last two mentioned embodiments of the device folds are produced which run screw like. A screw-like outer and inner main fold is thereby located on each upper and lower side.
To assist the production of the folds in a further embodiment it is proposed that an excess and/or under pressure can be applied from outside onto the gas bag surface whereby the excess and under pressure can be applied to the gas bag surface through openings in the folding dishes or interspaces between the folding dishes.
The invention will now be explained in further detail with reference to the embodiments shown in the drawings.